17-hydroxypregnenolone + NAD+ => pregn-5-ene-3,20-dione-17-ol + NADH + H+ 17-Hydroxypregnenolone and NAD+ react to form pregn-5-ene-3,20-dione-17-ol and NADH + H+. This reaction is catalyzed by the 3 beta-hydroxysteroid activity of 3-beta-hydroxysteroid dehydrogenase/isomerase (HSD3B) enzyme associated with the endoplasmic reticulum membrane. The active form of the enzyme is a homodimer. The enzyme occurs in two isoforms that are similar in their biochemical properties but differ in their tissue expression: type I (HSD3B1) is found in placenta and skin, while type II (HSD3B2) is found in the adrenal glands and gonads. 17-Hydroxypregnenolone is dehydrogenated to form pregn-5-ene-3,20-dione-17-ol Authored: Jassal, B, 2008-10-01 13:18:42 EC Number: 1.1.1.145 Edited: Jassal, B, 2007-04-20 21:09:56 Pubmed12832414 Pubmed1944309 Pubmed2243100 Pubmed2770297 Reactome Database ID Release 43196372 Reactome, http://www.reactome.org ReactomeREACT_10031 Reviewed: D'Eustachio, P, 2007-04-20 21:11:21